CPS Energy aims for 15-minute rolling blackouts in case of more grid trouble this winter

Long-term weather predictions indicate freezing temperatures like on Feb. 15 unlikely

SAN ANTONIO – As San Antonio’s city-owned utilities prepare for another winter, they’ve been taking steps to ensure the city isn’t left as vulnerable as it was during the February freeze.

“If another event happens this winter, which we’re all praying that it doesn’t, but if it does, there would likely be load shed,” said CPS Energy Chief Grid Optimization and Resiliency Officer Paul Barham. “It would not be in the same manner that they experienced during Uri.”

Like most of the state, San Antonio struggled with water and power issues during the February freeze. The cold temperatures put many power generating units off-line, even as Texans turned up their thermostats to get warm - pushing the statewide power grid toward a dangerous imbalance between supply and demand.

In the early hours of Feb. 15, the grid’s operator, the Electric Reliability Council of Texas (ERCOT), ordered CPS Energy and other power companies to start load-shedding - purposely cutting power to customers to avoid a catastrophic failure across the grid.

CPS Energy instituted rolling power outages, but only on a portion of its circuits. The outages weren’t applied evenly, though, and some residents suffered without power for hours at a time. A CPS Energy map of the circuits tapped for outages showed that some were out for less than an hour during the freeze, while others were off for nearly two-and-a-half days in total.

This map, included in the final report for the Committee on Emergency Preparedness, shows the uneven outage time across the circuits that were tapped for rotating outages. (CPS Energy)

Following the freeze, Mayor Ron Nirenberg formed the Committee on Emergency Preparedness to examine what happened. The committee ended up making numerous recommendations for both CPS Energy and SAWS on how to better prepare for a similar emergency in the future.

Part of those recommendations included improving CPS Energy’s load-shedding system. Barham said the utility didn’t have enough circuits available during the freeze to meet it’s load-shedding need.

The utility has since added 100 to 150 additional circuits into its load shed routine to better spread the burden instead of hammering an unlucky few with extended outages, he said.

“We have made significant improvements in our systems and the capacity for our ability to manage load shed where it has just, hopefully, the most minimal impact on our customers,” Barham said. “The target is 15 minute outages for a customer, followed by some period of hopefully hours of having power will be the design.”

In an event like the February freeze, Barham said a customer might just have power back for 15 minutes at a time, but “that’s kind of at the peak, at the worst of it.”

Whether CPS and its customers have to cope with rotating outages again will depend on how much stress is put onto the statewide grid.

Fortunately, long-term weather predictions at the moment indicate a similar freeze is unlikely this season.

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About the Authors:

Garrett Brnger is a reporter with KSAT 12.

Luis Cienfuegos is a photographer at KSAT 12.